PA-1 amps

[leonski]

TVs are terrific radiators and producers of RFI.
Make sure to keep as many cables far from the set as well as electronics.

Up for a test? Take an ordinary AM radio. A litttle handheld portable should do it.

With TV OFF tune into a local station. Clear is best. THAN turn the set ON. If you hear interference, you can now be sure ti's from the TV.
Set has several switching PS as well as high frequency 'stuff' inside.
If the problem gets worse when nearing the set and diminishes when further away, you're on the the CAUSE.   Solution may be tougher.

My former Panasonic Plasma, while not interferring with the stereo right next to it, would wipe out AM radio reception fo the 20' to 30' distance.

[lcheetec]

Thanks, appreciate the post and info.

I thought I'd solved it, with that cable isolator thing, but I didn't. I then had a brainwave, that maybe it was the cable analog audio connections to the BasX PT-100 pre, so k replaced that with an optical digital one. Nope.

I had the TV on while listening to music just, and the bloody thing was still singing (noise).

Turned off the TV, it's deadly quiet now.

Now to figure out what I can throw out or move..... it's going to be a long journey. But worth it (I think).

[lcheetec]

r.tapatalk.com/shareLink?url=http%3A%2F%2Fwww%2Extremeplace%2Ecom%2Fyabbse%2Findex%2Ephp%3Ftopic%3D224976%2E0&share_tid=224976&share_fid=38562&share_type=t

One of the best posts I've read, about isolating what seems to be noise from RFI/EMI, and not ground loop sources.

Just wanted to share.

Jul 28, 2018 18:18:14 GMT -5 lcheetec said:

Thanks, appreciate the post and info.

I thought I'd solved it, with that cable isolator thing, but I didn't. I then had a brainwave, that maybe it was the cable analog audio connections to the BasX PT-100 pre, so k replaced that with an optical digital one. Nope.

I had the TV on while listening to music just, and the bloody thing was still singing (noise).

Turned off the TV, it's deadly quiet now.

Now to figure out what I can throw out or move..... it's going to be a long journey. But worth it (I think).

[leonski]

With the problem apparently (Stess....Apparently) islolated to RFI from the TV, it now comes down to lead dress and distance.

I'd have to see what's going on and the physical setup.

This will require some time and a logical approach to trouble shooting. For example? If wires MUST cross, they should do so at Right Angles.

I'd replace RCA with Optical where feasible. My small dish connects to one of my DACs that way which eliminates ANY possiblilty of RFI or some kind of grounding nightmare.

So many things occur to me to try that I'd start with the solutions which DO NOT cost any MONEY.

Maybe start with a Bare Bones system. TV and basic sound system. THAN add stuff BACK to the system ONE THING at a time and listen for RFI to return.

Try to isolate thru distance if you can.

KEEP RECORDS so you know aht you've done and what needs to be done yet. Have a Beer.

[atto127]

I have just received my pa-1 amplifiers. I am very impressed with the sound. However I have been trying to connect my unbalanced preamplifier to them. However the provided connector does not work. The balanced preamplifier works great. Is there something wrong with the provided adapter?

[leonski]

You should read the manual about this connection setup. To use the balanced on SOME amps, as single ended (RCA connect) you need to bridge a pair of the balanced pins. One of the 'hot' pins to ground. Since balanced is 3 pins, one of 'em is ground, one is PLUS (+) and the 3rd is MINUS (-).
Does the amp come with a way to bridge pins? It'd be a little 'jumper' piece.
There are some pitfalls associated with this connection.

ANY real reason NOT to stick to the balanced connection? Audibly better or worse? The B&O ASC module is a balanced design and if the preamp is 'real' balanced might benefit from this connection.

The only OTHER thing I can think of is a Massive Long Shot, which is that the PRE amps ground / hot on the single ended connection out are somehow 'swapped'.......

[garbulky]

Aug 25, 2018 7:59:01 GMT -5 atto127 said:

I have just received my pa-1 amplifiers. I am very impressed with the sound. However I have been trying to connect my unbalanced preamplifier to them. However the provided connector does not work. The balanced preamplifier works great. Is there something wrong with the provided adapter?

I would contact Emotiva by phone.

[KeithL]

We thoroughly test each PA-1 before we ship it... but we hadn't been bothering to test the adapters.

However, since you are the second person to get a bad adapter, we'll be testing them from now on.

(Just call in to support and we'll arrange to send you another one.)

Aug 25, 2018 7:59:01 GMT -5 atto127 said:

I have just received my pa-1 amplifiers. I am very impressed with the sound. However I have been trying to connect my unbalanced preamplifier to them. However the provided connector does not work. The balanced preamplifier works great. Is there something wrong with the provided adapter?

[leonski]

Keith:
THe manual isn't specific. What pin is what on the XLR? which is +? Which is - and which is Ground?

Could the adaptors have a WIRE SWAPPED internally?

[jimk1963]

Aug 27, 2018 13:10:45 GMT -5 KeithL said:

We thoroughly test each PA-1 before we ship it... but we hadn't been bothering to test the adapters.

However, since you are the second person to get a bad adapter, we'll be testing them from now on.

(Just call in to support and we'll arrange to send you another one.)

Aug 25, 2018 7:59:01 GMT -5 atto127 said:

I have just received my pa-1 amplifiers. I am very impressed with the sound. However I have been trying to connect my unbalanced preamplifier to them. However the provided connector does not work. The balanced preamplifier works great. Is there something wrong with the provided adapter?

Just purchased 3 PA-1's for HT LCR, to be fed from Yamaha RX-A3050 RCA outputs. Ordered Sunday night, arriving in CA this Friday. Based on some folks having issues with the included RCA-XLR adapter, purchased 3 of these on Amazon for about $6 each:  "Hosa GXM-133 RCA to XLR3M Adaptor". These are cable-less adapters, you supply the RCA cable. Since I've also read that some folks are having hum issues, purchased another back-up in cable form, "JOLGOO Dual XLR Male to Dual RCA Male Cable". Hoping that Emotiva's just work OOB so I can return these, but we'll see. One other comment - I see folks on multiple threads making the following comment: "why are you bothering with single-ended RCA at all? You should be using balanced XLR all the way."  Well, sure. For those who happen to have XLR on their back panels, congrats. That's about 1% of the HT gear out there. For the rest of us, an RCA-XLR conversion is required.

[leonski]

A hum-free single ended -> balanced connection might best consist of a transformer system.

www.head-fi.org/threads/need-to-convert-single-ended-input-to-balanced-input-how.555150/

Might be a solution in this post.........

[Deleted]

Aug 28, 2018 17:19:35 GMT -5 jimk1963 said:

Aug 27, 2018 13:10:45 GMT -5 KeithL said:

We thoroughly test each PA-1 before we ship it... but we hadn't been bothering to test the adapters.

However, since you are the second person to get a bad adapter, we'll be testing them from now on.

(Just call in to support and we'll arrange to send you another one.)

Just purchased 3 PA-1's for HT LCR, to be fed from Yamaha RX-A3050 RCA outputs. Ordered Sunday night, arriving in CA this Friday. Based on some folks having issues with the included RCA-XLR adapter, purchased 3 of these on Amazon for about $6 each:  "Hosa GXM-133 RCA to XLR3M Adaptor". These are cable-less adapters, you supply the RCA cable. Since I've also read that some folks are having hum issues, purchased another back-up in cable form, "JOLGOO Dual XLR Male to Dual RCA Male Cable". Hoping that Emotiva's just work OOB so I can return these, but we'll see. One other comment - I see folks on multiple threads making the following comment: "why are you bothering with single-ended RCA at all? You should be using balanced XLR all the way."  Well, sure. For those who happen to have XLR on their back panels, congrats. That's about 1% of the HT gear out there. For the rest of us, an RCA-XLR conversion is required.

Please report back your observations of that setup. I also have an A3050 and am considering a trio of PA-1s for the LCR speakers. Would be very curious to hear your results.

[KeithL]

A balanced connection has two signal pins (signal + and signal -) and one ground.

The 1/4" input on the PA-1 is also balanced (it has three pins).

The RCA adapter typically just sends the input signal to one of the signal pins and grounds the other one.

And, yes, a simple little passive adapter really is the best way to do it.

Op amps require power - and add at least some noise.

Transformers always add some phase shift, distortion, and frequency response alteration.

Cheap transformers are terrible; and even pretty good ones are quite expensive; and they are subject to picking up hum.

The cheap little passive adapters really are the best way to go.

I've never cut open one of our adapters.

Some of them have actual wires inside, so a wire could be swapped or missing.

Others just have a single metal strip that makes contact with the connector pin at each end.

Aug 27, 2018 17:53:50 GMT -5 leonski said:

Keith:
THe manual isn't specific. What pin is what on the XLR? which is +? Which is - and which is Ground?

Could the adaptors have a WIRE SWAPPED internally?

[KeithL]

Transformers have far too many drawbacks to be practical in most situations these days .

ALL transformers introduce noise, distortion, and phase shift.

With cheap transformers these can be really bad.

Even good transformers are far from perfect; and can cost quite a lot (up to several hundred dollars).

Transformers are also very sensitive to picking up hum.

And, again, cheap transformers tend to have poor shielding, and reasonably well shielded ones tend to be more expensive.

If you have ground loop or isolation issues, then a transformer may help; otherwise they are best avoided.

Always try a nice cheap passive adapter FIRST.

Aug 28, 2018 20:40:44 GMT -5 leonski said:

A hum-free single ended -> balanced connection might best consist of a transformer system.

www.head-fi.org/threads/need-to-convert-single-ended-input-to-balanced-input-how.555150/

Might be a solution in this post.........

[leonski]

Cheap to the point of compromising the ultimate end is nearly ALWAYS a disaster.

I wonder if such a device could be made using a custom TOROID? They are pretty quiet in practical use.

[novisnick]

Aug 29, 2018 12:31:42 GMT -5 leonski said:

Cheap to the point of compromising the ultimate end is nearly ALWAYS a disaster.

I wonder if such a device could be made using a custom TOROID? They are pretty quiet in practical use.

My new monoblock amplifier  power supply!  😋

[KeithL]

In most situations like this, with audio signals, there is simply no justification for messing around with transformers.

If you have a source with a balanced output, and an amp with a balanced input, then the best option is a balanced cable.

(Unless you're in a noisy environment it probably won't make any difference, but it couldn't hurt, and it's cheap insurance against common-mode noise.)

If your source is unbalanced, and you don't have an especially long cable run, or an especially noisy environment, there is simply no benefit to converting the signal to balanced.

The PA-1 performs very well with either a balanced or unbalanced input.

There are good transformers, and really bad transformers, but ALL transformers introduce distortion, noise, and phase shift.

Even ignoring the price, adding a transformer into the signal path is going to do more harm to the signal than simply connecting your unbalanced signal to one input leg and grounding the other.

The idea that transformers are a good choice goes back a very long time - back when things were different - and dinosaurs tubes ruled the world.

Back then, noise was a major issue, and transformers, while they contribute distortion, phase shift, and potentially hum, do NOT contribute to raising the noise floor.

Transformers also provide ground isolation and a good transformer can exhibit exceptional common mode noise rejection.

Taken together, all these factors make an input transformer a great way to connect a low-impedance microphone to the input on a tube microphone preamp.

With a typical tube microphone preamp, minimizing noise is a major issue, while the input impedance is extremely high.

Therefore, by using a transformer with a high winding ratio, you can boost the level of the signal from the microphone without adding any noise ("free gain".)

This works because the input impedance of the preamp is extremely high (in the megohms).

Likewise, the output of the microphone is very low, and so sensitive to noise, but almost all of the noise it is likely to pick up is common mode hum, and transformers reject common mode hum extremely well.

(A modern condenser microphone is more likely to pick up hiss from its internal preamp; and, unlike common mode hum, a transformer won't help that at all.)

All of these benefits far outweigh the costs of using an input transformer IN THIS PARTICULAR SITUATION.

Long ago I owned a ribbon microphone, which had a 100 Ohm output impedance, and an absurdly low output voltage; and a tube microphone preamp that had high quality input transformers.

Together they were exceptionally quiet, even with long microphone cables, with relatively poor shielding, in relatively noisy locations.

In that combination, those cute little transformers (at about $100 each) were an excellent choice.

However, with modern equipment, the benefits simply aren't there.

Under normal circumstances, you will get equal or better performance by simply connecting your unbalanced source to one pin on the balanced input and grounding the other.

In this situation, it is the transformer that is the bigger compromise, because it carries too many disadvantages.

If you doubt this, find the best and most expensive transformer you can, and compare its specifications to those of a six inch length of copper wire.

Aug 29, 2018 12:31:42 GMT -5 leonski said:

Cheap to the point of compromising the ultimate end is nearly ALWAYS a disaster.

I wonder if such a device could be made using a custom TOROID? They are pretty quiet in practical use.

[jimk1963]

Aug 29, 2018 10:03:58 GMT -5 @balthazar2k4 said:

Aug 28, 2018 17:19:35 GMT -5 jimk1963 said:

Just purchased 3 PA-1's for HT LCR, to be fed from Yamaha RX-A3050 RCA outputs. Ordered Sunday night, arriving in CA this Friday. Based on some folks having issues with the included RCA-XLR adapter, purchased 3 of these on Amazon for about $6 each:  "Hosa GXM-133 RCA to XLR3M Adaptor". These are cable-less adapters, you supply the RCA cable. Since I've also read that some folks are having hum issues, purchased another back-up in cable form, "JOLGOO Dual XLR Male to Dual RCA Male Cable". Hoping that Emotiva's just work OOB so I can return these, but we'll see. One other comment - I see folks on multiple threads making the following comment: "why are you bothering with single-ended RCA at all? You should be using balanced XLR all the way."  Well, sure. For those who happen to have XLR on their back panels, congrats. That's about 1% of the HT gear out there. For the rest of us, an RCA-XLR conversion is required.

Please report back your observations of that setup. I also have an A3050 and am considering a trio of PA-1s for the LCR speakers. Would be very curious to hear your results.

Will do. Amps are in CA, scheduled for delivery tomorrow. May or may not have time to get them connected this weekend..

Reminds me, another "thing" that I see talked about endlessly but as a EE I'm so skeptical of - "burning in" these modern solid state amps. A smattering of Class D reviews out there claim that the amps sounded cold/sterile/"hard edged" until some random burn-in period. Some say 24 hours, one guy claimed 100 hours was needed. For me, there has to be clear science around this, and I just don't see it, with one exception - noisy capacitors. I've literally heard certain capacitor types sing (piezoelectric effect) over the years of designing cellular radios, but past that it's hard to imagine solid state circuits changing their characteristics after a short run-in. I'm open to be enlightened, please have at it. I'm sure there are golden audio best practices that include selection of high quality components to avoid all manner of audible sin. I'm just not fully clear on those techniques I guess.

[leonski]

The potential 'physics' reason for an amp burning in at least in the SHORT TERM is something called 'capacitor forming'.

My Magnepans were NEW IN BOX when I set them up. For about the first 5 hours or so, the stereo image shifted randomly back / forth.

They have never done so again. Once thru that 'phase', it was FINI. The only potential reason I could come up with was capacitor forming.

[KeithL]

Speakers are mechanical - and DO have mechanical parameters that change during the first few hours of use.

The rubber surrounds on speakers, as well as the spiders, soften up as they flex back and forth for the first few hours.

This can affect the audible performance significantly; especially in tuned enclosures, where the tuning is going to be calculated based their parameters AFTER they've been running a while.

While capacitors do change slightly over the first few hours of use, most modern designs tend not to be greatly affected by this, so that tends to be much less of a factor.

And that is likely to be even more true with a Class D design like the PA-1.

Aug 31, 2018 13:00:37 GMT -5 leonski said:

The potential 'physics' reason for an amp burning in at least in the SHORT TERM is something called 'capacitor forming'.

My Magnepans were NEW IN BOX when I set them up. For about the first 5 hours or so, the stereo image shifted randomly back / forth.

They have never done so again. Once thru that 'phase', it was FINI. The only potential reason I could come up with was capacitor forming.